Approach 1

import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

public class UppercaseExample {
    public static void main(String[] args) {
        // Original list of strings
        List<String> words = Arrays.asList("hello", "world", "java", "stream");

        // Convert each string to uppercase using Stream API
        List<String> uppercasedWords = words.stream()
                                            .map(String::toUpperCase)
                                            .collect(Collectors.toList());

        // Print the result
        System.out.println("Uppercased words: " + uppercasedWords);
    }
}

Approach 2

import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

public class MappingExample {
    public static void main(String[] args) {
        List<String> words = Arrays.asList("hello", "world", "java", "stream");

        List<String> uppercasedWords = words.stream()
            .collect(Collectors.mapping(
                String::toUpperCase,
                Collectors.toList()
            ));

        System.out.println("Uppercased words: " + uppercasedWords);
    }
}